The present invention concerns a procedure and apparatus for producing an a.c. voltage.
In particular in small combustion engine-driven generators producing a sinusoidal a.c. voltage, it is difficult to manage simultaneously both constant frequency and amplitude under changing load conditions because the frequency, and often also amplitude, are determined by speed of rotation exclusively. The speed is controlled using a centrifugal regulator or another mechanical governor, which in order to react requires a fairly large change in speed of rotation. Moreover, exact attainment of the correct frequency often requires separate measurement and continuous monitoring. Achieving a good sinusoidal waveform requires shaping the generator windings and air gaps in a way deviating from a design which is required to obtain maximum output power. As a result, the bulk of the generator increases and the weight increases in relation to the power output achieved.